1. Field of the Invention
This invention relates to a film retrieving apparatus for retrieving images recorded in the frames of a film such as a microfiche.
2. Description of the Prior Art
In a reader or the like wherein an image recorded in each frame of a microfilm such as a microfiche or a film jacket is projected onto a screen and read, use is made of a retrieving apparatus in which a card-like film such as a microfiche is carried on a carrier table, which is driven by an electric moving mechanism to thereby move a desired frame to the projecting position. The retrieving apparatus of this type has the function of automatically moving a designated frame to the projecting position or moving frames one by one to the projecting position, by operating a keyboard.
In a retrieving apparatus having the function of effecting the browsing retrieval in which the image of each frame is read by repeating the operation of moving frames in succession to the projecting position, stopping the frame at the projecting position for a predetermined time, and thereafter moving the microfilm to thereby move the next frame to the projecting position, if a film having a frame in which no image is recorded (hereinafter referred to as the blank frame) is used, the blank frame is stopped at the projecting position for the predetermined time. Thus, this blank frame is projected onto the screen for the predetermined time and the user wastes time until the next image is retrieved. Particularly, where a number of blank frames are present in the microfilm, wasteful work is done for a long time, and this has led to the problem of poor working efficiency. Also, where the blank frame is transparent, if this blank frame is projected onto the screen, the screen becomes very bright, and this has led to the problem that the user's eyes are fatigued.
Now, in some card-like microfilms such as microfiches or film jackets, there are slight deviations of the positions of frames or in some cases, the necessity of projecting a particular portion of the film such as a portion extending over two frames arises, and for this reason, the above-described retrieving apparatus is endowed with the fine position adjusting function for slightly moving the position of the film to thereby obtain a desired projection image.
There are the following two types of fine frame position adjusting mechanism of the film retrieving apparatus of this type:
(a) The type is which a carrier table carrying a film thereon is manually moved to accomplish fine adjustment; and
(b) The type in which a key for fine adjustment is provided on a keyboard for effecting the operation of moving a carrier table carrying a film thereon and by operating this key for fine adjustment, the carrier table is slowly moved in a vertical direction or a horizontal direction by an electric moving mechanism to thereby accomplish fine adjustment.
However, such prior art has the following problems: The case of the manual movement of item (a) above:
Rotating and sliding mechanisms for fine adjustment are required, and this leads to complexity of the entire mechanism. The manual operation permits the speed of movement of the carrier table to be adjusted as desired, but where a frame of a film of great information reduction rate is projected onto the screen by the use of a lens of high magnification, the image on the screen moves greatly under the influence of hand vibration and therefore, fine adjustment is difficult and requires skill. Also, the image reduction rate differs from film to film and correspondingly, the film form such as the number of frames in a film differs from film to film and therefore, where a film of the film form having a high reduction rate and a great number of frames is to be projected, it is necessary to use a lens of high magnification. In such case, the image on the screen moves greatly under the influence of hand vibration and therefore, fine adjustment is difficult and requires skill. The case of the electric operation of item (b) above:
While the key for fine adjustment is depressed, the carrier table is moved in a vertical direction or a horizontal direction, and when the key is released, the carrier table is stopped and therefore, anybody can easily operate the apparatus, but since the carrier table is moved at a predetermined speed independently of the magnification of the projection lens, the speed of movement of the image on the screen differs depending on the magnification of the projection lens. Accordingly, to project of film of the film form having a high reduction rate or a great number of frames, it is necessary to use a lens of high magnification, and in such a case, the speed of movement of the image on the screen becomes high and alignment of each frame is difficult and also, if the retrieving work is done for a long time, the user's eyes become fatigued or the user sometimes comes to feel as if he were seasick. Conversely, to project a card-like film of the film form having a low reduction rate or a small number of frames, use is made of a lens of low magnification, and in such case, the speed of movement of the image on the screen becomes low and therefore, the adjustment of the position of the frame requires a long time.